Shot count

If you are filling to 3600psi then your efficiency (based on 3660 start, 1900 end) is 1.16fpe/cuin. While not "stellar" this is (imho) quite respectable at 53+FPE.

The 100 shots (w/25.4's) at 875 the efficiency would be 1.26fpe/cuin, but at only 43+FPE.

The way to better optimize it would be with just your hammer spring. If you are doing 840 at max, back the HS out till your velocity starts dropping see how far you go. If your hammer spring is at max you can likely back it out and not see any drop in FPS at all. Once you reach the HS needed to get the pellet to 840 (at 131bar) any additional HS only causes wasted air, and larger ES. Hitting the valve harder causes more air of the valve, but it is air that useless as the pellet has already left the barrel.

Or since the Impact has an adjustable regulator, try turning the reg pressure up, at the same hammer spring setting and see if the FPS increases. If the velocity increases with no change in the hammer spring then your hammer spring is not tuned for the 131 bar.

If you have the gun tuned for efficiency at 131 bar, then a regulator increase to 135 bar should result in a decrease in FPS.

I'll reiterate what BinTinBoat said but in my own way.

Your issue is likely being too close to the plateau of your FPS/FPE for your regulator setting. 131 bar is kind of low for 33.95's @ 850~ fps...I would recommend setting the regulator at 140~ bar and you'd likely see an efficiency increase upwards of 1.3 fpe/ci...which is generally the efficiency people get when they tune to the Knee of their power curve, ie: 4-5% from peak velocity, which means you want to be shooting them at 890-900 fps peak and back the power wheel / hammer spring down till you get to 845~

When/if you turn up the regulator you will have to smack the valve a bit harder to get the same power due to it being more difficult to open from the extra pressure against the poppet.

-Matt

Find your peak velocity with the 33.95's. If it is below 890-900 fps then you want to turn up the reg until it does in 5~ bar increments. So I would go to 135 and test if you can't hit that velocity at 131. with power wheel at max. Then move up to 140 if 135 doesn't do it. IMO

"ackuric"Find your peak velocity with the 33.95's. If it is below 890-900 fps then you want to turn up the reg until it does in 5~ bar increments. So I would go to 135 and test if you can't hit that velocity at 131. with power wheel at max. Then move up to 140 if 135 doesn't do it. IMO

Click to expand...

Right now, since his hammer spring is at MAX, he is at max velocity for 131bar.

Easiest way to tune it is to decide what velocity you want. Say it's 890
Leave your hammer spring at max at raise the regulator pressure by 5 bar and retest. If the velocity is not 900, then keep raising the reg pressure 5 bar at a time until you get 900 fps. Now leave the reg at this pressure setting and turn your hammer spring back a 1/4 turn and retest. Keep turning the hammer spring back until you get to 890. This is where you should be tuned for max efficiency at 890fps.

I am not sure if the hammer on max is the same as the power wheel on max as I don't have an impact but if that is the case then he will definitely need to raise his reg pressure up to at least 140 bar to operate at 845~ fps with the 33.95's efficiently in his current set up.